A novel dual-mode (DM) dielectric waveguide (DW) filter with controllable transmission zeros (TZs) is presented. The DM filter is based on a cascaded implementation, utilizing individual dual-mode DW cavities. The filter is practically realized by embedding three circular blind holes at different positions in the surface of a dielectric silver coated square cavity. By changing the relative position of the blind holes or rotating the direction of the proposed DW cavity, the filter’s TZs’ frequency locations can be flexibly adjusted. The zero points can be set in frequency at the low end of the passband, at the high end of the passband, or they can be generated at both the low and high ends of the passband in order to improve the selectivity of the filter. In this study, the two-cavity fourth-order filter is taken as an example, and the experimental results validate the feasibility of the presented theoretical design.

This paper designs a vertically polarized, horizontal, omnidirectional vehicle antenna for the mobile communication band, covering the available frequency bands of the wireless sensor network and 5G. The antenna is composed of semi-T monopole and semicone monopole, which are placed vertically on the metal plate, especially suitable for being mounted on top of a car. T-branch mainly works at low frequency, and cone branch mainly works at high frequency. The cone branch adopts tapered structure in order to improve the impedance matching of antenna and increase the bandwidth of antenna. The antenna can be miniaturized by cutting the antenna in half. The operating frequencies of the antenna are 770 MHz–1000 MHz and 1.7 GHz–3.78 GHz which can cover multiple wireless system bands, including GSM, LTE, and 5G.

A simple structure concentric annular-ring slot dual-band circularly polarized (CP) microstrip antenna operating at ISM band (2.45 GHz) and 5G band (3.5 GHz) is proposed in this paper. The antenna achieves dual-band operation by digging two concentric annular-ring slots on the ground. And on the angular positions with 45 degrees inclined of each annular slot, two bent structures are loaded to generate circularly polarized radiation. The radiation of this antenna is bidirectional, and the directions of rotation are opposite. The measured results of the annular-ring slot microstrip antenna show good performance of dual-band circularly polarized characteristics.

A novel design approach to wideband, dual-resonant microstrip annular sector patch antenna (MASPA) is proposed. As mathematically revealed by the dominant eigen-equation, MASPA with increased backfire radiation can be evolved from a truncated microstrip leaky-wave antenna. Then, the general relationships between the ratios of outer/inner radii, flared angles, and operational modes are deduced. The outer arc of the annular sector patch is set as a magnetic wall or open-circuited while the inner one is set as an electric wall or short-circuited, such that the patch’s size could be accordingly reduced by 13% to the circular sector case. As finally validated, a dual-resonant MASPA with a flared angle of 150°, outer/inner radii ratio of 3.0, and backfire gain up to 4.0 dBi can be implemented on single-layered air substrate with a height of 0.043-wavelength at the center frequency. Therefore, the advanced design approach can effectively realize patch miniaturization, wide band, and increased backfire radiation without inquiring extra multiple radiators and incorporating any additional reactance compensation techniques.